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coroutine-lock: convert CoQueue to use QemuLockable 

There are cases in which a queued coroutine must be restarted from
non-coroutine context (with qemu_co_enter_next).  In this cases,
qemu_co_enter_next also needs to be thread-safe, but it cannot use
a CoMutex and so cannot qemu_co_queue_wait.  Use QemuLockable so
that the CoQueue can interchangeably use CoMutex or QemuMutex.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20180203153935.8056-4-pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
This commit is contained in:
Paolo Bonzini 2018-02-03 10:39:33 -05:00 committed by Fam Zheng
parent e70372fcaf
commit 1a957cf9c4
2 changed files with 12 additions and 6 deletions
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6
include/qemu/coroutine.h
View File

@ -183,7 +183,9 @@ void qemu_co_queue_init(CoQueue *queue);
* caller of the coroutine. The mutex is unlocked during the wait and
* locked again afterwards.
*/
void coroutine_fn qemu_co_queue_wait(CoQueue *queue, CoMutex *mutex);
#define qemu_co_queue_wait(queue, lock) \
qemu_co_queue_wait_impl(queue, QEMU_MAKE_LOCKABLE(lock))
void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock);
/**
* Restarts the next coroutine in the CoQueue and removes it from the queue.
@ -271,4 +273,6 @@ void coroutine_fn qemu_co_sleep_ns(QEMUClockType type, int64_t ns);
*/
void coroutine_fn yield_until_fd_readable(int fd);
#include "qemu/lockable.h"
#endif /* QEMU_COROUTINE_H */

12
util/qemu-coroutine-lock.c
View File

@ -40,13 +40,13 @@ void qemu_co_queue_init(CoQueue *queue)
QSIMPLEQ_INIT(&queue->entries);
}
void coroutine_fn qemu_co_queue_wait(CoQueue *queue, CoMutex *mutex)
void coroutine_fn qemu_co_queue_wait_impl(CoQueue *queue, QemuLockable *lock)
{
Coroutine *self = qemu_coroutine_self();
QSIMPLEQ_INSERT_TAIL(&queue->entries, self, co_queue_next);
if (mutex) {
qemu_co_mutex_unlock(mutex);
if (lock) {
qemu_lockable_unlock(lock);
}
/* There is no race condition here. Other threads will call
@ -60,9 +60,11 @@ void coroutine_fn qemu_co_queue_wait(CoQueue *queue, CoMutex *mutex)
/* TODO: OSv implements wait morphing here, where the wakeup
* primitive automatically places the woken coroutine on the
* mutex's queue. This avoids the thundering herd effect.
* This could be implemented for CoMutexes, but not really for
* other cases of QemuLockable.
*/
if (mutex) {
qemu_co_mutex_lock(mutex);
if (lock) {
qemu_lockable_lock(lock);
}
}